Fenoterol, 5-[1-hydroxy-2[[2-(4-hydroxyphenyl)-1-methylethyl]-amino] ethyl]1,2-benzenediol, is a β2-adrenergic receptor agonist that has traditionally been used for the treatment of pulmonary disorders such as asthma. This drug has two chiral (asymmetric) carbons that can each be independently arranged in an R or S configuration, so that the drug exists in distinct (R,R), (R,S), (S,R) and (S,S) forms known as stereoisomers. Fenoterol is commercially available as a racemic mixture of the (R,R)- and (S,S)-compounds.
Fenoterol is known to act as an agonist that binds to and activates the β2-adrenergic receptor. This activity has led to its clinical use in the treatment of asthma because this agonist's activity dilates constricted airways. Additional therapeutic uses for fenoterol remain to be thoroughly explored. Pharmacological studies of the class of drugs that includes fenoterol have shown that only one of the enantiomers is responsible for generating brochodilation. For example, studies have demonstrated that the primary bronchodilatory activity for racemic (±)-fenoterol resides in the (R,R)-isomer of fenoterol. Further, it has recently become apparent that the inactive enantiomer may be associated with adverse effects. For instance, the diastereomer (S,S)-fenoterol has been demonstrated to cause adverse side effects or development of tolerance often associated with β2-adrenergic receptor agonist treatment.
It would therefore be advantageous to provide fenoterol compositions that were effective at treating disorders such as asthma, chronic obstructive pulmonary disease, or congestive heart failure, but had reduced side effects such as hypersensitivity and drug resistance (tolerance).